Urge to support adult in company (5)
I believe the answer is:
along
'in company' is the definition.
(I've seen this in another clue)
'urge to support adult' is the wordplay.
'urge' becomes 'long' (an urge is a longing).
'to support' says to put letters next to each other (in a down clue, some letters hold others up).
'adult' becomes 'a' (abbreviation).
'long' put after 'a' is 'ALONG'.
(Other definitions for along that I've seen before include "Lengthwise" , "(Going) in company (with others)" , "By the side of" , "Sea monster, opposite Charybdis" , "Beside - as groups often sing!" .)